Researchers from Shandong Transportation Institute and Jinan Transportation Development Center have demonstrated that incorporating waste tire rubber powder into asphalt significantly improves its low-temperature performance and broadens its viscoelastic temperature interval. Published in Frontiers in Materials in November 2026, the original research article utilizes dynamic mechanical thermal analysis to characterize the phase-transition properties of various asphalt binders. The study highlights the potential of using recycled tire rubber as a value-added modifier in eco-friendly pavement materials, offering a sustainable approach to enhancing road durability while addressing environmental concerns associated with waste tire disposal.
The investigation focused on the viscoelastic behavior of asphalt, a material that exhibits significant temperature sensitivity and transitions through glassy, viscoelastic, and viscous states. Understanding these phase transitions is critical for engineering applications, as the performance of asphalt mixtures in road pavements is directly related to these rheological states. The researchers employed dynamic mechanical thermal analysis to examine the effects of heating rate and loading frequency on the phase-transition characteristics of asphalt. This technique allows for the continuous measurement of dynamic mechanical parameters over a wide temperature range, providing a comprehensive view of the material’s behavior that static tests cannot easily achieve.
The study compared neat asphalt, styrene-butadiene-styrene modified asphalt, and rubber asphalt prepared using a wet-mix process. The rubber asphalt was created by mixing A-grade road asphalt with 22 weight percent crumb rubber powder derived from waste truck tires. The crumb rubber, with a particle size of 60 to 80 mesh, was used without chemical pretreatment or surface modification. The selection of the 22 percent rubber content was based on preliminary tests showing that this ratio achieved an elastic recovery value of 74.0 percent, meeting the specification requirement of at least 70 percent for softening points higher than 60 degrees Celsius.
Experimental procedures involved temperature scanning tests conducted at fixed frequencies, strain levels, and heating rates. The researchers determined that the asphalt remained within the linear viscoelastic range when the strain level was below 0.049 percent. The heating rates varied from 1 to 4 degrees Celsius per minute, while loading frequencies ranged from 1 to 20 hertz. The results indicated that the temperature spectrum of mechanical response parameters and the phase-transition temperature shift to higher temperatures with increasing heating rates and loading frequencies.
The phase-transition temperature was defined using characteristic points derived from the complex modulus and loss modulus curves. The temperature corresponding to the midpoint of the complex modulus curve was designated as T0, while T1 and T2 represented the intersections of the midpoint tangent with the low-temperature and high-temperature asymptotes, respectively. The glass transition temperature, Tg, was identified as the peak temperature of the loss modulus curve. The researchers found that heating rate and the logarithmic value of loading frequency exhibit a linear relationship with the phase-transition temperature. A three-dimensional spatial relationship model was established to predict the phase-transition temperature under various test conditions, assuming independent and linearly additive effects of heating rate and loading frequency.
For low-temperature performance evaluation, T1, T0, and Tg were used as dynamic indicators. The ranking of these indicators was consistent with the results from the bending beam rheometer tests, which are standard in the performance grading framework. Rubber asphalt demonstrated superior low-temperature performance compared to both neat asphalt and styrene-butadiene-styrene modified asphalt. This finding suggests that the addition of waste tire rubber powder significantly enhances the resistance of asphalt to low-temperature cracking, a primary factor influencing pavement failure in cold climates.
The viscoelastic temperature interval, defined as the range between T1 and T2, provides a phase-transition-based candidate service temperature interval for asphalt. Within this interval, asphalt remains in the viscoelastic state, exhibiting both deformation resistance and elastic recovery capability. The study found that incorporating styrene-butadiene-styrene modifiers or rubber powder into neat asphalt effectively broadened the viscoelastic temperature interval. Rubber asphalt exhibited the widest viscoelastic temperature interval of 37.9 degrees Celsius, compared to approximately 32 degrees Celsius for styrene-butadiene-styrene modified asphalt and about 28 degrees Celsius for some neat asphalts. This wider interval suggests that rubber-modified asphalt can maintain its viscoelastic properties over a broader range of service temperatures.
For high-temperature performance evaluation, the study noted that neat asphalt and modified asphalt require separate analysis based on T2. The T2 values of modified asphalts were lower than those of some neat asphalts, which appeared inconsistent with their higher softening points and performance grading high-temperature grades. The researchers explained this inconsistency by noting that the introduction of modifiers changes the phase-transition behavior of asphalt. The polymer network or rubber particles can shift the viscous-flow transition to a lower temperature while increasing stiffness and elastic recovery at high temperatures. Therefore, T2 should be regarded as a complementary phase-transition indicator rather than a direct measure of high-temperature performance or rutting resistance.
The study acknowledged several limitations, including the use of only two parallel tests for each asphalt sample and the lack of differential scanning calorimetry or mixture-level performance tests. The multi-factor model was based on two single-factor experiments rather than an independent full-factorial design, meaning the interaction between heating rate and loading frequency was not independently evaluated. The relationship between phase-transition temperatures and actual pavement performance was not directly validated. The researchers recommended future studies include long-term aging tests, microstructural characterization using techniques such as Fourier-transform infrared spectroscopy and atomic force microscopy, and rheological validation using independent methods.
The findings underscore the importance of dynamic mechanical thermal analysis in evaluating the viscoelastic properties of asphalt. By providing a detailed characterization of phase-transition temperatures, the study offers a scientific basis for selecting asphalt binders that can withstand varying environmental conditions. The use of waste tire rubber powder not only improves the mechanical performance of asphalt but also aligns with circular economy principles by valorizing waste materials. As the demand for sustainable infrastructure materials grows, the integration of recycled rubber into pavement construction presents a promising avenue for enhancing both the durability and environmental profile of road networks.
The study utilized a TA Instruments DMA Q800 apparatus equipped with a double-cantilever fixture to conduct the temperature scanning tests. The instrument’s furnace system provided steady-state temperature-control accuracy of ±0.1 °C, while the dynamic ramp thermal offset remained within ±0.5 °C. To ensure the temperature sensor provided a representative sample temperature, it was positioned close to the specimen. Prior to testing, the instrument underwent both absolute-temperature and dynamic-temperature calibration, the latter using a standard polycarbonate specimen to compensate for thermal lag. The researchers noted that while furnace chamber accuracy is high, it cannot fully eliminate transient intra-sample temperature gradients for low-thermal-conductivity asphalt specimens under dynamic heating. This instrumental limitation is a key factor in the observed shifts of modulus curves toward higher temperatures at increased heating rates, alongside the intrinsic temperature dependence of the viscoelastic relaxation process.
Specimens for the dynamic mechanical thermal analysis were prepared via a casting method using molds that produced samples with dimensions of 60 mm in length, 13 mm in width, and 3 mm in depth. The asphalt was poured into the molds, allowed to cool at room temperature for at least one hour, and then scraped level. The samples were subsequently cooled in a refrigerator for 30 minutes before the molds were removed. Each asphalt sample was tested in two parallel trials, with the average value and the range between replicates calculated to assess repeatability. The ranges between the two replicates for the characteristic temperatures T1, T0, T2, and Tg were generally within 0.3 °C to 2.5 °C, indicating acceptable repeatability for the dynamic mechanical measurements.
The mathematical modeling of the phase-transition temperatures involved fitting the complex modulus curve with a Boltzmann function and the loss modulus curve with a BiGaussian function. The Boltzmann function was used to extract T1, T0, and T2, with a coefficient of determination exceeding 0.99 for the SBS1 asphalt. The standard errors for the fitted parameters x0 and dx were generally less than 0.5 °C and 0.3 °C, respectively. For the loss modulus, the BiGaussian function was chosen because the curve is asymmetric, with a steeper rise on the low-temperature side and a more gradual decay on the high-temperature side. The fitting quality for the BiGaussian function was high, with R2 values greater than 0.98, and the standard error of the peak temperature Tg was generally less than 2.5 °C. These functions served as empirical tools to determine characteristic temperatures rather than constitutive models for the material.
The selection of the 22 wt.% crumb rubber content for the rubber asphalt was driven by specific performance criteria outlined in the Specification for Asphalt Rubber Pavement and Construction in China. Preliminary tests at 18 wt.%, 20 wt.%, and 22 wt.% yielded elastic recovery values of 65.2%, 68.9%, and 74.0%, respectively. The specification requires an elastic recovery of at least 70% when the softening point is higher than 60 °C. The 22 wt.% mixture met this requirement and achieved a PG76-28 grade. The crumb rubber used was obtained from waste truck tires with a particle size of 60–80 mesh. It was processed by removing visible impurities such as wood chips, gravel, glass, and dirt, but no chemical pretreatment or surface modification was applied. The key physical and chemical indices of the crumb rubber included a relative density of 1.16, an ash content of 6.8%, and a carbon black content of 31.2%.
The bending beam rheometer tests provided a comparative benchmark for the dynamic mechanical thermal analysis results. The BBR results showed that asphalt binders with lower Tg values, such as the rubber asphalt and SBS3, generally exhibited lower creep stiffness S and higher creep-rate parameter m at the same test temperature. For instance, the rubber asphalt had a Tg of -19.7 °C in the DMTA data and a BBR S value of 158 MPa at -18 °C. In contrast, neat asphalt A1, with a higher Tg, showed a BBR S value of 252 MPa at -6 °C. This agreement between the DMTA-derived Tg ranking and the BBR results supports the use of Tg as a complementary dynamic indicator of low-temperature performance, although it is not a replacement for established low-temperature tests.
Subject of Research: Waste tire rubber powder enhances Asphalt’s low-temperature performance and viscoelastic temperature interval as revealed by dynamic mechanical thermal analysis
Article Title: Waste tire rubber powder enhances Asphalt’s low-temperature performance and viscoelastic temperature interval as revealed by dynamic mechanical thermal analysis
Article References: Gao, B., Wang, Y., Liu, Z., Wang, G., Liu, Q., & Wang, X. (2026). Waste tire rubber powder enhances Asphalt’s low-temperature performance and viscoelastic temperature interval as revealed by dynamic mechanical thermal analysis. Frontiers in Materials, 13, Article 1972351. https://doi.org/10.3389/fmats.2026.1972351
Image Credits: AI Generated
DOI: 10.3389/fmats.2026.1972351
Keywords: Waste, tire, rubber, powder, enhances, Asphalt, low-temperature, performance, viscoelastic, temperature, interval, revealed
News Source: Denise Maddox. (November 7, 2026). Rubber Powder Broadens Asphalt’s Viscoelastic Temperature Range. Scienmag.
